There's a really easy way to convert any units to other units.
Right now, we have the fraction (4 miles) / (2 hours).
We want to find a fraction that's exactly equal to that one,
but has the units of (miles/minute) or maybe (feet/minute).
Just take the original fraction, and multiply it by some other
fractions.
Each fraction you multiply it by must have the value of ' 1 ' so
you don't change the value of the original fraction. But it can
have different units, that cancel with other units to eventually
give you the units you want.
(4 miles / 2 hours) times (1 hour / 60 minutes)
The second fraction is equal to ' 1 ', because the top and the bottom
have the same value ... 1 hour is the same thing as 60 minutes.
Multiply the fractions: (4 miles x 1 hour) / (2 hour x 60 minutes)
Now you can cancel 'hour' from the top and the bottom, and you have
(4 miles x 1) / (2 x 60 minutes)
= (4 miles) / (120 minutes)
= (4 / 120) mile/minute = 0.0333... mile / minute .
Let's do it again, go a little farther, and get an answer that
might mean more and feel more like an answer.
(4 miles) / (2 hours) x (5280 feet / mile) x (1 hour / 60 minutes)
The 2nd and 3rd fractions both have the value of ' 1 ', because
the top is equal to the bottom.
Multiply all three fractions:
(4 miles x 5280 feet x 1 hour) / (2 hours x 1 mile x 60 minutes)
You can cancel both 'mile' and 'hour' out of the top and bottom,
and look what you have left:
(4 x 5280 feet x 1) / (2 x 1 x 60 minutes)
= (4 x 5280) / (2 x 60) feet / minutes
= (21,120 / 120) feet/minute = 176 feet per minute
